I agree with Leed and Farmergirl - this needs to be handled by a professional. An 11 yr old shouldn't be having a phone which allows him internet access 24/7 or any other internet device which allows him privacy. Any devices also need a parental filter, so if he types inappropriate things in, it'll be blocked. His parent also needs to have an age appropriate talk about sex and some morals such as - you need to be an adult to have sex, never force anyone and you need to love the person before you engage in sex. The parent needs to have this sex talk because he's already seen way too much at this point. He needs to clearly understand you don't touch anyones private parts. Don't ignore this problem. Sorry this is happening.